I understood most of the material, and I guess that thinking about the fourth dimension in terms of coordinates is helpful, but the chapter didn't make too much of an impression on me. The concept that most interested me was that of the golden ratio, and I was sorry that so few words were devoted to the subject. I would have at least liked to have seen a picture of the spiral of golden rectangles with an accompanying picture of a chambered nautilus. Or Agoniatites, a relative of the modern chambered nautilus. I did like the sunflower picture, though, and the picture of cubes in a dodecahedron.
The most interesting part of the coordinate stuff was the section on complex numbers. I learned about i in high school, but I don't think we got much farther than memorizing the results of i ^2, etc. The graph of complex numbers on page 172 provided my first sense of the reality of imaginary numbers, if that makes any sense. They are much easier to understand when presented in a two-dimensional format.